1. Field
The disclosed embodiments relate generally to telecommunication networks, and more specifically to assigning grant channels to mobile stations in such networks.
2. Background
A High Data Rate (HDR) subscriber station or mobile station (MS), referred to herein as an access terminal, may be mobile or stationary, and may communicate with one or more HDR base stations (BS), referred to herein as modem pool transceivers. An access terminal transmits and receives data packets through one or more modem pool transceivers to an HDR base station controller, referred to herein as a modem pool controller. Modem pool transceivers and modem pool controllers are parts of a network called an access network. An access network transports data packets between multiple access terminals. The access network may be further connected to additional networks outside the access network, such as a corporate intranet or the Internet, and may transport data packets between each access terminal and such outside networks. An access terminal that has established an active traffic channel connection with one or more modem pool transceivers is called an active access terminal, and is said to be in a traffic state. An access terminal that is in the process of establishing an active traffic channel connection with one or more modem pool transceivers is said to be in a connection setup state. An access terminal may be any data device that communicates through a wireless channel or through a wired channel, for example using fiber optic or coaxial cables. An access terminal may further be any of a number of types of devices including but not limited to PC card, compact flash, external or internal modem, or wireless or wireline phone. The communication link through which the access terminal sends signals to the modem pool transceiver is called a reverse link. The communication link through which a modem pool transceiver sends signals to an access terminal is called a forward link.
In various system configurations of the HDR access network, the base station (BS) may use individual Grant Channels (GCH) to issue mobile station (MS)-specific grants, such as Reverse Enhanced Supplemental Channel (R-ESCH) grants. According to these system configurations, an individual GCH may carry information for a single MS only. Thus, if more than one MS needs to be scheduled simultaneously in a particular time slot, then more than one GCH must be used. The number of grant channels used is determined by the number of mobile stations that can be simultaneously scheduled in the same time slot, and also by the existence of a common grant channel.
Accordingly, to ensure mobile stations are notified about the grants, each mobile station can monitor every individual one of the grant channels. In that case, as long as the number of mobile stations scheduled in a time slot does not exceed the number of grant channels, each scheduled mobile station can be notified about the grant. This monitoring of every individual grant channel, however, requires each mobile station to monitor a relatively large number of parallel code channels, and increases the complexity of the mobile station processing. To reduce the required processing in the mobile stations, a subset of the grant channels can be assigned to each mobile station for monitoring. However, requiring the mobile station to monitor only a subset of the grant channels means that there may be times when not every scheduled mobile station can be notified about the grant. This expected performance loss, comprising the failure of GCH notification, is referred to herein as a “GCH outage” and is due to conflicts between the assigned subsets.
It should be apparent from the discussion above that there is a need for efficient notification of grant channels to each mobile station such that each mobile station monitors less than all available individual grant channels. The present invention satisfies this need.